Diesel combustion control with digital rate shaping

Abstract

Due to the impact of the transport industry on the environment, stringent emission norms are being pushed for implementation. The real challenges for OEM’s are to keep up with the regulations. The transition to complete electric future is still distant, and the existing diesel engines must survive for at least 5-10 years. Therefore, OEM’s must achieve the legislative requirements with fuel consumption benefits using the available technology. One of the techniques available is diesel combustion control with digital rate shaping. Therefore, the thesis will investigate this method with triple pilot injection strategy and study the improvements in terms of fuel efficiency and emissions. The work is carried out in two different parts; first, the Injector capabilities were tested in FIE (Fuel Injection Equipment) test rig at different load points with shorter and longer dwell times for different fuel quantities at different rail pressures. The aim was to investigate for injector performance in terms of minimum possible dwell time, fuel quantity, repeatability, and robustness of the injector. Resultsshow inconsistent injector performance. Second, the combustion is studied in a single-cylinder test rig. The test was investigated for one specific load point. The Injector capabilities and boundary conditions for triple pilot injection were again tested. Based on the Rate of heat release curve, each parameter, i.e. dwell time, fuel quantities and rail pressures were manually varied. Next, design of experiments (DoE) was set up using ETAS ASCMO. Running the DoE point in single-cylinder test rig, a combustion model was created from this data. Dwell time, fuel quantities and rail pressure as input parameters different response curves were created to see effects of these parameters on emissions, bsfc and combustion noise. These curves are then used to define a calibration strategy. Optimisations performed in the software are verified in the single-cylinder test rig. The optimised injection strategy was validated in Gen IV Volvo multi-cylinder production engine. The results replicate the inconsistent performance of injector seen in FIE test rig and do not justify the supplier claim. However, based on the trend a description about how to efficiently balance the calibration to achieve lowest engine out emissions, combustion noise and achieve efficiency through model-based calibration is proposed.